Studies of the process of testosterone dependent masculinization of the central nervous system will be studied in rat fetuses of normal mothers and of mothers exposed to a regimen of stress that results in a failure of behavioral masculinization. Aromatization will be quantified in vitro in individual hypothalamic and amygdaloid nuclear regions from day 17 post-conception through postnatal day five. Cytochemical techniques will be used to quantify delta 5-3betaol-steroid dehydrogenase and glucose-6-phosphate dehydrogenase (type I hydrogen) in Leydig cells of fetuses of normal and stressed mothers. Quantitative cytochemistry will also be used to localize and quantify RNA, glucose-7-phosphate dehydrogenase and cytochrome P450 in hypothalamic and amygdaloid nuclei of fetuses of both sexes of control and stressed mothers. In some experimental groups, we will measure plasma LH levels by radioimmunoassay and determine the timing of appearance of hypothalamic GnRH and of pituitary LH by immunocytochemistry.